1. Field of the Invention
The present invention relates to a control circuit and a protection control system, and more particularly relates to a control circuit and a protection control system with synchronous protection.
2. Description of Related Art
FIG. 1 is a schematic diagram of a conventional control system. Each control circuit 10 comprises an under-voltage lockout circuit 15 coupled to an input power source Vin. The input power source Vin supplies electric power to the control circuit 10. The under-voltage lockout circuit 15 determines whether a voltage level of the input power source Vin is over low or not according to an under-voltage protection level Vuo for preventing the control circuit 10 from operating incorrectly. The under-voltage lockout circuit 15 outputs an under-voltage lockout signal UVLO to make the control circuit 10 enter an under-voltage lockout protection mode so as to stop operating until the voltage level of the input power source Vin is recovered to a sufficiently high voltage level from the over-low voltage level.
However, due to process errors, the corresponding voltage levels (the time points) of the input power source Vin at which the respective control circuits 10 enter the under-voltage lockout protection mode are different, thus it is quite likely to result in that some of the control circuits 10 enter the under-voltage lockout protection mode and other control circuits 10 do not enter the under-voltage lockout protection mode. The aforementioned asynchronous under-voltage lockout protection (to which similar problems also may happen to other protection functions) causes the control circuits to be operated uncoordinatedly, thus easily resulting in unpredictable operation errors or damages.